In the opportunistic yeast Candida albicans, as with all fungi, a considerable part of the metabolism is derived toward the synthesis of wall polysaccharides whose organization finely modulates the adaptation of the cell to the medium. Numerous research teams have established the preponderant importance of the mannans of C. albicans in the physiopathology of candidiasis. It has been demonstrated that the diverse interactions of mannans with the humoral and cellular components of the host are based on a specificity dependent on the oligomannosides sequences synthesized by the yeast. It is the bond anomery of the mannose residues and the length of the oligomannoside chain which determine the nature of the interaction which influences the outcome of the infection.
Research concerning the biological properties and the structure of these oligomannosides, as well as the development of diagnostic methods or preventive procedures for these infections, requires the availability of large amounts of oligomannosides. However, the production of natural oligomannosides from strains of C. albicans is complicated and expensive. It is, of course, necessary to have available such strains, to store them, and culture them in fermenters under very standardized conditions because the nature of the sugars is strictly dependent on the medium, temperature, oxygenation, culture time, etc. The fermenter culturing of C. albicans requires sophisticated expertise and numerous precautionary measures of a microbiological nature. The batches of mannans must then be recovered from the cultures and characterized by their antigenic and especially chemical properties. This requires depolymerization of the mannans and NMR analysis of the liberated sugars.
These natural oligomannosides are used to prepare immunological diagnostic tests of C. albicans infections. However, sensitization of the plates with the mannans antigen is performed with different production batches and according to a protocol which does not enable monitoring of the amount deposited. Thus, several tests use natural yeast mannans for the diagnosis of candidiasis (Sendid, B. et al., 1999, J. Clin. Microbiol. 37(5): 1510–7) and Crohn's disease (Sendid, B. et al., 1996, Clin. Diagn. Lab. Immunol. 3(2): 219: 26). These tests detect antibodies directed against the mixtures of oligomannoside sequences present in the mannans of C. albicans and S. cerevisiae. 